Pipe with valve
 

I'm trying to model a 3d inviscid flow, with liquid water, inside a pipe ended with valve.

At first the valve is open (with pressure outlet) and I use the steady solver to get a steady solution.

Then the valve has to be suddenly closed, so by using the steady solution as initial condition and changing the outlet to wall I can obtain an unsteady solution.

The problem is that I expect an increasing gauge pressure, while I get a fluctuating gauge pressure around zero in the closed pipe and I don't understand the reason.

By making the same test with air I get a similar result with constant density, while by using ideal gas density I get an increasing gauge pressure.

Any suggestion or reference will be really appreciated!!!

Thanks in advance!!!

GB

PS:I'm using the UDF of the manual for water density and speed sound and a constant mass-flow-inlet.